1. Field of Invention:
This invention relates generally to pin switches which are actuatable by a swingable door or other movable closure member to open a normally-closed electrical circuit, and more particularly to a universal switch of this type which can be tailored in length to meet the particular requirements of various installations and which can be vertically mounted.
2. Status of Prior Art:
The function of a pin switch is to break an electrical circuit when the switch comes into physical contact with a movable member at a predetermined position of this member, and to close the circuit when the member is shifted to another position. To carry out this function, the pin switch is provided with a pin or rod that when pressed in by the movable member effects disengagement of normally-closed switch contacts.
Pin switches are commonly used in refrigerators and electric ovens, the switch being so installed that when the hinged door of the refrigerator or oven is swung open to provide access to the interior, the switch then closes to complete a circuit to a lamp illuminating the interior. But when the door is thereafter shut, it then presses in the actuator pin of the switch, thereby opening the switch and turning off the light so that the interior of the refrigerator or oven is no longer illuminated.
Pin switches are also used in conjunction with automobile security systems to set off an alarm when the hood of the engine compartment or the lid of the trunk is forced open by an intruder. In a security installation, the system is put in its active mode by the owner before he leaves the vehicle, say, at a parking site. The pin switch is so placed in relation to the hinged trunk lid or engine compartment hood that the switch is in an open state when the trunk lid or hood is fully closed. But if the trunk lid or hood is thereafter forced open while the security system is in its active mode, the resultant closing of the pin switch triggers the security system to set off the alarm.
One practical problem encountered with pin switches is that each installation requires a pin length that puts the mounted pin switch in proper operative relation to the door, trunk lid or whatever other movable member is involved in the installation. If, therefore, one wishes to retrofit automobiles with a security system that requires a lid-actuated pin switch, the proper pin length depends on the trunk structure. And since this structure is not standardized for all cars and varies from model to model, the installer in order to cope with this situation must have available a large inventory of different pin switch sizes from which he can select the size appropriate to the installation being worked on.
Pin switches are commercially available in a range of pin lengths, and if the installer carries in inventory the full range of pin lengths, he will not be faced with a problem. But as is more often the case, the installer has a limited inventory of pin switches in different lengths, he may find that he lacks the particular length necessary to a given installation.
To meet the need for a universal pin switch that can be tailored to assume a proper pin length that satisfies a particular installation requirement, the patent to Kanbar, U.S. Pat. No. 4,775,768, whose entire disclosure is incorporated herein by reference, discloses a pin switch whose pin is in the form of an insulation rod having a front section in a corrugated formation to define a series of equi-spaced annular grooves, each marking an increment of rod length. In order to tailor the pin switch so that its effective length is appropriate to the requirements of a given installation, the user simply snips off the front section at the groove marking the desired length.
The practical difficulty with a Kanbar-type pin switch in which the switch is provided with a mounting plate at right angles to the pin is that it best lends itself to mounting on a horizontal brace or other horizontal surface in the trunk or engine compartment of an automobile. When so mounted, the insulation rod or pin then lies on a vertical axis so that it can be engaged by the hinged hood or trunk lid when it is closed.
However, the typical hinged hood in an automobile has a front edge that is somewhat curved; hence when the hood swings down to its fully closed position, the edge which then engages the pin of the switch travels in an arcuate path that is angled with respect to the vertical axis along which the pin is shiftable. As a consequence, the hood edge seeks to displace the switch pin from its vertical path and in doing so it may cause the pin switch to bend and break or malfunction.
Moreover, in many modern automobiles, absent in the engine compartment or in the trunk is a horizontal brace or other horizontal surface on which a Kanbar-type pin switch can be mounted. Hence this switch does not lend itself to installation in such a vehicle.
Because the mounting plate of the Kanbar-type pin switch is normal to the pin, when the switch is mounted on a vertical wall, the pin is then at right angles to the wall. For this reason, the Kanbar-type pin switch is not usable on a vehicle-mounted tool box, on step vans, repair trucks, enclosed trailers, recreational vehicles, mobile homes, and in other applications where a hinged door, lid or other closure meets a vertical wall at right angles thereto. If one were to mount a Kanbar-type switch on the vertical wall, its pin would be at right angles to this wall and would therefore not be engaged by the closure.
Of prior art interest are the U.S. patents to Kallage, Jr., et al., U.S. Pat. No. 3,821,529; Boosey, U.S. Pat. No. 1,112,760; King, Jr., U.S. Pat. No. 3,835,615; Fraser, U.S. Pat. No. 3,251,971, and the German patent No. 3,320,455 to Marten.